This invention relates in general to the control of particles and dust generated by rotary tools and, more particularly to a dust collecting shield for rotary sanders and the like.
Rotary hand tools, such as grinders, pad sanders, flap sanders, tuck pointing blades etc. generate a considerable quantity of particles and fine dust from the object being ground or sanded and from the sanding media itself. Grinders and sanders may be used with such materials as fiberglass, metal, wood, plastics, carbon fibers, and the like. The fine particulate material generated may be a health hazard to the operator and those in the vicinity. Wood dust and hot metal particles can be a fire hazard. Particles of the material being ground and occasionally small pieces of the grinding or sanding media may be ejected at high velocity under centrifugal forces.
A large variety of different shields have been developed for controlling dust and chips produced by hand-held rotary grinding, sanding, carving and polishing machines using an abrasive disc, pad or other shape. Many use a circular bowl-shaped housing surrounding the rotating disc, held to the tool by a clamp, bolt, etc., as exemplified by the shields described by Buser et al. in U.S. Pat. No. 5,125,190 and Isakson in U.S. Pat. No. 3,862,521. Generally, a tube is secured in communication with the shield interior to permit connection of a vacuum system for drawing off dust.
While effective for containing and removing dust during simple operations, such as surface grinding or sanding, these shields have a number of problems.
With prior shields it is difficult or impossible to fit a wrench to the arbor section of the tool to change the abrasive disc without first removing the shield. This is very inconvenient, in particular where a series of abrasive discs using gradually finer grit are to be used in finishing a surface.
Most prior shields are a one piece molding or fabricated shield combining a base, a skirt extending from the base around the abrasive disc and a collar or other means for attachment to the tool. Because of this, a separate and distinct shield assembly must be provided for every abrasive disc diameter or backing pad thickness and for every different sanding tool collar size. Distributors of such shields must maintain a large inventory of different size shield assemblies, requiring large amounts of retail floor space and stockroom space, and a large capital investments to stock a complete selection of products. The consumer must be very carefully to obtain a shield that matches his tool by make and model.
One-piece shield designs must use materials having strength and rigidity optimized for the most highly stressed portion of the shield. This limits the flexibility that is highly desirable in some areas, in particular the collar to shield base region to permit the shield skirt and base to flex slightly.
Prior shield designs have a fixed exhaust tube fastened to and communicating with the interior of the shield for connection to a vacuum system. Typically, the exhaust tube is connected through the shield base, as shown by Matechuk in U.S. Pat. No. 4,782,632 or tangentially to the shield skirt, as shown by Rudiger in U.S. Pat. No. 4,135,334. While effective for many purposes, the fixed exhaust tubes often require the use of adapters for connection to vacuum hoses of different diameters or will require a series of different complete shield assemblies for use with different vacuum systems. Also, the location of the fixed exhaust tube may make use by left-handed persons or use in some applications difficult with prior lightweight, one-piece, flexible shields. Where the vacuum hose to be used is large or heavy, the weight of the hose may pull on the shield, distorting the shape of the shield skirt and reduce dust collection efficiency.
In most cases a clear plastic skirt is preferred to allow observation of operation through the shield. Where sanding metal, plastic may have insufficient strength and resistance to flying metal particles, requiring the use of a metal base and skirt.
Prior shield systems are optimized for use with one, or a small range, of abrasive disc designs. When a different disc design is used, the entire shield must be replaced. Distributors must maintain separate inventories of shields for use with surface sanders, requiring a full circular shield, and shields for use with flap sanders, tuck pointing discs and the like that require a side opening of a particular width. In addition, when using a conventional abrasive disc shield for edge sanding, dust and other particles on the side of the disc opposite the work being abraded are not captured.
Thus, there is a continuing need for improvements in dust control systems for rotary abrasive tools that permit one shield assembly to be used with a variety of tools having different shaft housing diameters and with a variety of abrasive discs and the like, that allow the use of different materials in the collar and shield base/skirt areas and different collar designs and materials to permit a selected degree of shield flexibility in use, that permit the use of a variety of exhaust tube diameters, locations and vacuum hose support arrangements, that are adaptable to use with both surface abrading and side abrading systems and capture dust from the top and bottom surfaces of a side abrading system, and that allow the use of shield components of different materials with different resistance to particle impact and that permit use of one shield with a variety of abrasive disc systems.